Detecting platelets in a blood sample

ABSTRACT

Apparatus and methods are provided including imaging a blood sample that is a cell suspension deposited in a sample chamber. The cells are allowed to settle in the sample chamber to form a monolayer of cells. At least one microscopic image is acquired of the monolayer of cells using a microscope ( 24 ) while the microscope is focused at a monolayer-depth-level, and a first platelet count of platelets that have settled within the monolayer, is determined. An additional microscopic image of the simple is acquired, while the microscope is focused at a different depth level from the monolayer-depth-level, and a second platelet count of platelets that have not settled within the monolayer is determined. An output is generated based upon the first and second platelet counts. Other applications are also described.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from U.S. Provisional Patent Application No. 62/946,998 to Yafin et al., filed Dec. 12, 2019, entitled “Detecting Platelets in a Blood Sample,” which is incorporated herein by reference.

FIELD OF EMBODIMENTS OF THE INVENTION

Some applications of the presently disclosed subject matter relate generally to analysis of bodily samples, and in particular, to optical density and microscopic measurements that are performed upon blood samples.

BACKGROUND

In some optics-based methods (e.g., diagnostic, and/or analytic methods), a property of a biological sample, such as a blood sample, is determined by performing an optical measurement. For example, the density of a component (e.g., a count of the component per unit volume) may be determined by counting the component within a microscopic image. Similarly, the concentration and/or density of a component may be measured by performing optical absorption, transmittance, fluorescence, and/or luminescence measurements upon the sample. Typically, the sample is placed into a sample carrier and the measurements are performed with respect to a portion of the sample that is contained within a sample chamber of the sample carrier. The measurements that are performed upon the portion of the sample that is contained within the sample chamber of the sample carrier are analyzed in order to determine a property of die sample.

SUMMARY OF EMBODIMENTS

In accordance with some applications of the present invention, a portion of a blood sample that comprises a cell suspension is placed within a sample chamber that is a cavity that includes a base surface. Typically, the cells in the cell suspension are allowed to settle on the base surface of tire sample chamber to form a monolayer of cells on the base surface of the sample chamber. Subsequent to the cells having been left to settle on the base surface of the sample chamber (e.g., by having been left to settle for a predefined time interval), at least one microscopic image of at least a portion of the monolayer of cells is typically acquired. Typically, a plurality of images of the monolayer are acquired, each of the images corresponding to an imaging field that is located at a respective, different area within the imaging plane of the monolayer. Typically, an optimum depth level at which to focus the microscope in order to image the monolayer is determined, e.g., using techniques as described in U.S. Pat. No. 10,176,565 to Greenfield, which is incorporated herein by reference. For some applications, respective imaging fields have different optimum depth levels from each other. For some applications, platelets that have settled within the monolayer are identified within the at least one microscopic image of at least a portion of the monolayer of cells.

The inventors of the present application have noticed that it is often the case that, even after having been left to settle such as to form a monolayer using the techniques described herein, not all of the platelets within a blood sample settle within the monolayer, and some cells continue to be suspended within the cell solution. More specifically, the inventors have found that it is typically the case that, even after the sample has been left to settle for approximately two minutes, between 10 percent and 70 percent of the platelets within the sample do not settle within the monolayer focus field. Typically, if the monolayer is allowed to form over a longer time period, then more platelets settle within the monolayer focus field. However, the inventors have found that even if the monolayer is allowed to form over a relatively long time period (e.g., between 15 and 30 minutes), some platelets still remain suspended within the solution such that the platelets ate not disposed within the monolayer focus field. Typically, the number of platelets that remain suspended within the solution (such that the platelets are not disposed within the monolayer focus field) is dependent on the time for which the monolayer is allowed to form, in addition to the height of the cavity in which the cell solution is placed.

Therefore, for some applications, in order to accurately estimate the number of platelets in the sample, platelets that arc suspended within the cell solution arc identified, in addition to identifying platelets within the monolayer focus field. Typically, such platelets are identified by focusing the microscope at additional depth levels to tire depth level(s) to which the microscope is focused in order to image the monolayer of cells (referred to herein as “the monolayer depth level(s)”), and acquiring images at the additional depth levels. Typically, the platelets within the images that are acquired at the additional depth levels are identified and counted, and, based upon the count of platelets within those images, a total count of the platelets that are suspended within the cell solution is estimated.

For some applications, a count of the platelets that have settled within the monolayer is compared to a count of the platelets that have not settled within the monolayer. Typically, an output is generated in response to the comparison. For some applications, a clinical condition is derived and outputted to a user, based upon the comparison of the count of the platelets that have settled within the monolayer and the count of the platelets that have not settled within the monolayer. For example, the extent of platelet activation within the sample may be derived, at least partially based upon the comparison. Alternatively or additionally, a clinical condition may be derived based upon the size, shape, settling time, and/or settling dynamics of the platelets. For some such applications, the settling dynamics of the platelets are determined by imaging the same imaging field a plurality of times, with a lime interval between each of the image acquisitions, and/or by determining until what height within the sample chamber platelets are present at a given time.

For some applications, a computer processor generates an output indicating that the sample should be prepared in a different way to how it was prepared (e.g., by modifying the diluent within which the sample is diluted, by adding a platelet activation agent, and/or by adding a coagulation agent), based upon the comparison.

For some applications, based upon the comparison between the count of the platelets that have settled within the monolayer and the count of the platelets that have not settled within the monolayer, the portion of the blood sample is invalidated from being used for performing at least some measurements upon the sample. For example, if the ratio of unsettled platelets to settled platelets is greater than a first given threshold, and/or lower than a second given threshold, then this might be interpreted as being indicative of a problem with the sample and/or the preparation thereof.

For some applications, a parameter of the sample (such as platelet volume, mean platelet volume, and/or median platelet volume) is determined based upon a measurement that is performed upon the portion of the sample. For some applications, the measurement is calibrated, based upon the comparison between properties of the platelets that have settled within the monolayer and properties of the platelets that have not settled within the monolayer.

There is therefore provided, in accordance with some applications of the present invention, a method including:

placing at least a portion of a blood sample that is a cell suspension within a sample chamber that is a cavity that includes a base surface:

-   -   allowing the cells in the cell suspension to settle on the base         surface of the sample chamber to form a monolayer of cells on         the base surface of the sample chamber;

acquiring at least one first microscopic image of at least a portion of the monolayer of cells, using a microscope while the microscope is focused at a monolayer-depth-level, at which the monolayer is within focus of the microscope;

identifying platelets that have settled within the monolayer, within the at least one microscopic image;

based upon the platelets that ate identified within the at least one microscopic image, determining a first platelet count of platelets that have settled within the monolayer;

acquiring at least one additional microscopic image of the portion of tire sample using the microscope, while the microscope is focused at a different depth level from the monolayer-depth-level;

identifying platelets that have not settled within the monolayer, within the at least one additional microscopic image;

-   -   based upon the platelets that ate identified within the at least         one additional microscopic image, determining a second platelet         count of platelets that have not settled within the monolayer;         and     -   generating an output based upon the first and second platelet         counts.

In some applications, the method further includes deriving an error with the blood sample at least partially based upon comparing the first and second platelet counts to each other, wherein generating the output includes generating an indication of the error.

In some applications, the method further includes deriving an error with preparation of the blood sample at least partially based upon comparing the first and second platelet counts to each other, wherein generating the output includes generating an indication of the error.

In some applications, the method further includes deriving a clinical condition of the subject at least partially based upon comparing the first and second platelet counts to each other, wherein generating the output includes generating an indication of the clinical condition.

In some applications, the method further includes deriving a measure of platelet activation at least partially based upon comparing the first and second platelet counts to each other, wherein generating the output includes generating an indication of the platelet activation.

In some applications, identifying platelets that have not settled within the monolayer within the at least one additional microscopic image includes accounting for interference with visibility of platelets by white blood cells that are disposed within the monolayer.

In some applications, identifying platelets that have not settled within the monolayer within the at least one additional microscopic image includes accounting for interference with visibility of platelets by red blood cells that are disposed within the monolayer.

In some applications:

acquiring the at least one first microscopic image of the portion of the monolayer of cells includes acquiring a first number of images of the monolayer at respective imaging fields while the microscope is focused at one or more monolayer-depth-levels, at which the monolayer is within focus of the microscope;

-   -   acquiring the at least one additional microscopic image of the         portion of the sample includes acquiring a second number of         images at respective imaging fields, while the microscope is         focused at the different depth level from the         monolayer-depth-level; and

a ratio between the first number and the second number is greater than 2:1.

In some applications:

acquiring the at least one additional microscopic image of the portion of the sample includes acquiring a plurality of additional microscopic images, while the microscope is focused at respective different depth levels from the monolayer-depth level; and

-   -   identifying platelets that have not settled within the monolayer         within the at least one additional microscopic image includes         avoiding duplicate counts of platelets within images that are         acquired at adjacent depth levels.

In some applications, avoiding duplicate counts of platelets within images that are acquired at adjacent depth levels includes accounting for lateral movement of platelets between acquisitions of the images that arc acquired at adjacent depth levels.

There is further provided, in accordance with some applications of the present invention, a method including:

placing at least a portion of a blood sample that is a cell suspension within a sample chamber that is a cavity that includes a base surface;

allowing the cells in the cell suspension to settle on die base surface of the sample chamber to form a monolayer of cells on the base surface of the sample chamber;

acquiring at least one microscopic image of at least a portion of the monolayer of cells, using a microscope while the microscope is focused at a monolayer-depth-level, at which the monolayer is within focus of the microscope;

identifying platelets that have settled within the monolayer, within the at least one microscopic image;

-   -   acquiring at least one additional microscopic image of the         portion of the sample using the microscope, while the microscope         is focused at a different depth level from the         monolayer-depth-level;     -   identifying platelets that have not settled within the         monolayer, within the at least one additional microscopic image;         and     -   generating an output at least partially based upon the platelets         identified as having settled within the monolayer and the         platelets identified as not having settled within the monolayer.     -   In some applications, the method further includes estimating a         platelet count for the blood sample based upon the platelets         identified as having settled within the monolayer and the         platelets identified as not having settled within the monolayer,         wherein generating the output includes generating an indication         of the platelet count.

In some applications, the method further includes deriving a platelet-settling characteristic of the sample based upon the platelets identified as having settled within the monolayer and the platelets identified as not having settled within the monolayer, wherein generating the output includes generating an indication of the platelet-settling characteristic.

In some applications, the method further includes deriving a characteristic of platelets within the sample based upon a combination of the platelets identified as having settled within the monolayer and the platelets identified as not having settled within the monolayer, wherein generating the output includes generating an indication of the derived characteristic.

There is further provided, in accordance with some applications of the present invention, a method including:

placing at least a portion of a sample that is a suspension within a sample chamber that is a cavity that includes a base surface;

allowing entities in the cell suspension to settle on the base surface of the sample chamber to form a monolayer of entities on the base surface of the sample chamber;

acquiring at least one microscopic image of at least a portion of the monolayer of entities, using a microscope while the microscope is focused at a monolayer-depth-level, at which the monolayer is within focus of the microscope;

-   -   identifying entities of a given type that have settled within         the monolayer, within the at least one microscopic image;

acquiring at least one additional microscopic image of the portion of the sample using the microscope, while the microscope is focused at a different depth level from the monolayer-depth level;

identifying entities of the given type that have not settled within the monolayer, within the at least one additional microscopic image; and

generating an output at least partially based upon the entities of the given type identified as having settled within the monolayer and the entities of the given type identified as not having settled within the monolayer.

There is further provided, in accordance with some applications of the present invention, apparatus including:

a sample chamber that is a cavity that includes a base surface and that is configured to receive at least a portion of a blood sample that is a cell suspension and to allow the cells in the cell suspension to settle on the base surface of the sample chamber to form a monolayer of cells on the base surface of the sample chamber;

a microscope configured to acquire:

-   -   at least one first microscopic image of at least a portion of         the monolayer of cells, while the microscope is focused at a         monolayer-depth-level, at which the monolayer is within locus of         the microscope, and     -   at least one additional microscopic image of the portion of the         sample, while the microscope is focused at a different depth         level from the monolayer-depth-level; and

a computer processor configured to:

-   -   identify platelets that have settled within the monolayer,         within the at least one first microscopic image,     -   determine a first platelet count of platelets that have settled         within the monolayer, based upon the platelets that are         identified within the at least one microscopic image,     -   identify platelets that have not settled within the monolayer,         within the at least one additional microscopic image,     -   determine a second platelet count of platelets that have not         settled within the monolayer, based upon the platelets that are         identified within the at least one additional microscopic image;         and     -   generate an output based upon the first and second platelet         counts.

There is further provided, in accordance with some applications of the present invention, apparatus including:

a sample chamber that is a cavity that includes a base surface and that is configured to receive at least a portion of a blood sample that is a cell suspension and to allow the cells in the cell suspension to settle on the base surface of the sample chamber to form a monolayer of cells on the base surface of the sample chamber;

a microscope configured to acquire:

-   -   at least one first microscopic image of at least a portion of         the monolayer of cells, while the microscope is focused at a         monolayer-depth-level, at which the monolayer is within focus of         the microscope, and     -   at least one additional microscopic image of the portion of the         sample, while the microscope is focused at a different depth         level from the monolayer-depth-level; and

a computer processor configured to:

-   -   identify platelets that have settled within the monolayer,         within the at least one first microscopic image,     -   identify platelets that have not settled within the monolayer,         within the at least one additional microscopic image, and     -   generate an output at least partially based upon the platelets         identified as having settled within the monolayer and the         platelets Identified as not having settled within the monolayer.

There is further provided, in accordance with some applications of the present invention, apparatus including:

a sample chamber that is a cavity that includes a base surface and that is configured to receive at least a portion of a sample that is a cell suspension and to allow the cells in the cell suspension to settle on the base surface of the sample chamber to form a monolayer of cells on the base surface of the sample chamber;

a microscope configured to acquire:

-   -   at least one first microscopic image of at least a portion of         the monolayer of cells, white the microscope is focused at a         monolayer-depth-level, at which the monolayer is within focus of         the microscope, and     -   at least one additional microscopic image of the portion of the         sample, while the microscope is focused at a different depth         level from the monolayer-depth-level; and

a computer processor configured to:

-   -   identify entities of a given type that have settled within the         monolayer, within the at least one first microscopic image,     -   identify entities of the given type that have not settled within         the monolayer, within the at least one additional microscopic         image, and     -   generate an output at least partially based upon the entities of         the given type identified as having settled within the monolayer         and the entities of the given type identified us not having         settled within the monolayer.

The present invention will be more fully understood from the following detailed description of embodiments thereof, taken together with the drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing components of a biological sample analysis system, in accordance some applications of the present invention;

FIGS. 2A, 2B, and 2C are schematic illustrations of an optical measurement unit, in accordance with some applications of the present invention;

FIGS. 3A, 3B, and 3C arc schematic illustrations of respective views of a sample carrier that is used for performing both microscopic measurements and optical density measurements, in accordance with some applications of the present invention;

FIGS. 4A and 4B are microscope images acquired from a monolayer depth level under brightfield imaging using respective imaging parameters, in accordance with some applications of the present invention;

FIG. 5 is a fluoroscopic microscope image acquired from the monolayer depth level, in accordance with some applications of the present invention;

FIGS. 6A and 6B are microscope images acquired from an additional depth level (i.e., not the monolayer depth level) under bright field imaging, using respective imaging parameters, in accordance with some applications of the present invention;

FIG. 7 is a fluoroscopic microscope image acquired from the additional depth level, in accordance with some applications of the present invention;

FIG. 8 is a flowchart showing steps of a method that is performed, in accordance with some applications of the present invention;

FIG. 9 is a flowchart showing steps of an additional method that is performed, in accordance with some applications of the present invention; and

FIG. 10 is a flowchart showing steps of a further method that is performed, in accordance with some applications of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Reference is now made to FIG. 1 , which is block diagram showing components of a biological sample analysis system 20, in accordance with some applications of the present invention. Typically, a biological sample (e.g., a blood sample) is placed into a sample carrier 22. While die sample is disposed in the sample carrier, optical measurements are performed upon the sample using one or more optical measurement devices 24. For example, the optical measurement devices may include a microscope (e.g., a digital microscope), a spectrophotometer, a photometer, a spectrometer, a camera, a spectral camera, a hyperspectral camera, a fluorometer, a spectrofluorometer, and/or a photodetector (such as a photodiode, a photoresistor, and/or a phototransistor). For some applications, the optical measurement devices include dedicated light sources (such as light emitting diodes, incandescent light sources, etc.) and/or optical elements for manipulating light collection and/or light emission (such as lenses, diffusers, filters, etc.).

A computer processor 28 typically receives and processes optical measurements that are performed by the optical measurement device. Further typically, the computer processor controls the acquisition of optical measurements that are performed by the one or more optical measurement devices. The computer processor communicates with a memory 30. A user (e.g., a laboratory technician, or an individual from whom the sample was drawn) sends instructions to the computer processor via a user interface 32. For some applications, the user interface includes a keyboard, a mouse, a joystick, a touchscreen device (such as a smartphone or a tablet computer), a touchpad, a trackball, a voice-command interface, and/or other types of user interfaces that arc known in the art. Typically, the computer processor generates an output via an output device 34. Further typically, the output device includes a display, such as a monitor, and the output includes an output that is displayed on the display. For some applications, the processor generates an output on a different type of visual, text, graphics, tactile, audio, and/or video output device, e.g., speakers, headphones, a smartphone, or a tablet computer. For some applications, user interface 32 acts as both an input interface and an output interface, i.e., it acts as an input/output interface. For some applications, the processor generates an output on a computer-readable medium (e.g., a non-transitory computer-readable medium), such as a disk, or a portable USB drive, and/or generates an output on a printer.

Reference is now made to FIGS. 2A, 2B, and 2C, which are schematic illustrations of an optical measurement unit 31, in accordance with some applications of tire present invention. FIG. 2A shows an oblique view of the exterior of the fully assembled device, while FIGS. 2B and 2C shows respective oblique views of the device with the cover having been made transparent, such components within the device are visible. For some applications, one or more optical measurement devices 24 (and/or computer processor 28 and memory 30) is housed inside optical measurement unit 31. In order to perform the optical measurements upon the sample, sample carrier 22 is placed inside the optical measurement unit. For example, the optical measurement unit may define a slot 36, via which the sample earner is inserted into the optical measurement unit. Typically, the optical measurement unit includes a stage 64, which is configured to support sample carrier 22 within the optical measurement unit. For some applications, a screen 63 on the cover of the optical measurement unit (e.g., a screen on the front cover of the optical measurement unit, as shown) functions as user interface 32 and/or output device 34.

Typically, the optical measurement unit includes microscope system 37 (shown in FIGS. 2B-C) configured to perform microscopic imaging of a portion of the sample. For some applications, the microscope system includes a set of light sources 65 (which typically include a set of brightfield light sources (e.g. light emitting diodes) that are configured to be used for brightfield imaging of the sample, a set of fluorescent light sources (e.g. light emitting diodes) that are configured to he used for fluorescent imaging of the sample), and a camera (e.g., a CCD camera, or a CMOS camera) configured to image the sample. Typically, the optical measurement unit also includes an optical-density-measurement unit 39 (shown in FIG. 2C) configured to perform optical density measurements (e.g., optical absorption measurements) on a second portion of the sample. For some applications, the optical-density-measurement unit includes a set of optical-density-measurement light sources (e.g., light emitting diodes) and light detectors, which are configured for performing optical density measurements on the sample. For some applications, each of the aforementioned sets of light sources (i.e., the set of brightfield light sources, the set of fluorescent light sources, and the set optical-density-measurement light sources) includes a plurality of light sources (e.g. a plurality of light emitting diodes), each of which is configured to emit light at a respective wavelength or at a respective hand of wavelengths.

Reference is now made to FIGS. 3A and 3B, which are schematic illustrations of respective views of sample carrier 22, in accordance with some applications of the present invention. FIG. 3A shows a top view of the sample carrier (the top cover of the sample carrier being shown as being opaque in FIG. 3A, for illustrative purposes), and FIG. 3B shows a bottom view (in which the sample carrier has been rotated around its short edge with respect to the view shown in FIG. 3A). Typically, the sample carrier includes a first set 52 of one or more sample chambers, which are used for performing microscopic analysis upon the sample, and a second set 54 of sample chambers, which arc used for performing optical density measurements upon the sample. Typically, the sample chambers of the sample carrier are filled with a bodily sample, such as blood via sample inlet holes 38. For some applications, the sample chambers define one or more outlet holes 40. The outlet holes are configured to facilitate filling of the sample chambers with the bodily sample, by allowing air that is present in the sample chambers to be released from the sample chambers. Typically, as shown, the outlet holes are located longitudinally opposite the inlet holes (with respect to a sample chamber of the sample carrier). For some applications, the outlet holes thus provide a more efficient mechanism of air escape than if the outlet holes were to be disposed closer to the inlet holes.

Reference is made to FIG. 3C, which shows an exploded view of sample carrier 22, in accordance with some applications of the present invention. For some applications, the sample carrier includes at least three components; a molded component 42, a glass layer 44 (e.g., a glass sheet), and an adhesive layer 46 configured to adhere the glass layer to an underside of the molded component. The molded component is typically made of a polymer (e.g., a plastic) that is molded (e.g., via injection molding) to provide the sample chambers with a desired geometrical shape. For example, as shown, the molded component is typically molded to define inlet holes 38, outlet holes 40, and gutters 48 which surround the central portion of each of the sample chambers. The gutters typically facilitate filling of the sample chambers with the bodily sample, by allowing, air to flow to the outlet holes, and/or by allowing the bodily sample to flow around the central portion of the sample chamber.

For some applications, a sample carrier as shown in FIGS. 3A-C is used when performing a complete blood count on a blood sample. For some such applications, the sample carrier is used with optical measurement unit 31 configured as generally shown and described with reference to FIGS. 2A-C. For some applications, a first portion of the blood sample is placed inside first set 52 of sample chambers (which are used for performing microscopic analysis upon the sample, e.g., using microscope system 37 (shown in FIGS. 2B-C)), and a second portion of the blood sample is placed inside second set 54 of sample chambers (which are used for performing optical density measurements upon the sample, e.g., using optical-density-measurement unit 39 (shown in FIG. 2C)). For some applications, first set 52 of sample chambers includes a plurality of sample chambers, while second set 54 of sample chambers includes only a single sample chamber, as shown. However, the scope of the present application, includes using any number of sample chambers (e.g., a single sample chamber or a plurality of sample chambers) within either the first set of sample chambers or within the second set of sample chambers, or any combination thereof. The first portion of the blood sample is typically diluted with respect to the second portion of the blood sample. For example, the diluent may contain pH buffers, stains, fluorescent stains, antibodies, sphering agents, lysing agents, etc. Typically, the second portion of the blood sample, which is placed inside second set 54 of sample chambers is a natural, undiluted blood sample. Alternatively or additionally, the second portion of the blood sample may be a sample that underwent some modification, including, for example, one or more of dilution (e.g., dilution in a controlled fashion), addition of a component or reagent, or fractionation.

For some applications, one or more staining substances are used to stain the first portion of the blood sample (which is placed inside first set 52 of sample chambers) before the sample is imaged microscopically. For example, the staining substance may he configured to stain DNA with preference over staining of other cellular components. Alternatively, the staining substance may be configured to stain all cellular nucleic acids with preference over staining of other cellular components. For example, the sample may be stained with acridine orange reagent. Hoechst reagent, and/or any other staining substance that is configured to preferentially stain DNA and/or RNA within the blood sample. Optionally, the staining substance is configured to stain all cellular nucleic acids but the staining of DNA and RNA are each more prominently visible under some lighting and filter conditions, as is known, for example, for acridine orange. Images of the sample may be acquired using imaging conditions that allow detection of cells (e.g., brightfield) and/or imaging conditions that allow visualization of stained bodies (e.g. appropriate fluorescent illumination). Typically, the first portion of the sample is stained with acridine orange and with a Hoechst reagent. For example, the first (diluted) portion of the blood sample may be prepared using techniques as described in U.S. Pat. No. 9,329,129 to Pollak, which is incorporated herein by reference, and which describes a method for preparation of blood samples for analysis that involves a dilution step, the dilution step facilitating the identification and/or counting of components within microscopic images of the sample. For some applications, the first portion of the sample is stained with one or more stains that cause platelets within the sample to be visible under brightfield imaging conditions and/or under fluorescent imaging conditions, e.g., as described hereinabove. For example, the first portion of the sample may be stained with methylene blue and/or Romanowsky stains.

Referring again to FIGS. 2B-C, typically, sample carrier 22 is supported within the optical measurement unit by stage 64. Further typically, the stage has a forked design, such that the sample carrier is supported by the stage around the edges of the sample carrier, but such that the stage does not interfere with the visibility of the sample chambers of the sample carrier by the optical measurement devices. For some applications, the sample carrier is held within the stage, such that molded component 42 of the sample carrier is disposed above the glass layer 44, and such that an objective lens 66 of a microscope unit of the optical measurement unit is disposed below the glass layer of the sample carrier. Typically, at least some light sources 65 that are used during microscopic measurements that are performed upon the sample (for example, light sources that are used during brightfield imaging) illuminate the sample carrier from above the molded component. Further typically, at least some additional light sources (not shown) illuminate the sample carrier from below the sample carrier (e.g., via the objective lens). For example, light sources that are used to excite the sample during fluorescent microscopy may illuminate the sample carrier from below the sample carrier (e.g., via the objective lens).

Typically, prior to being imaged microscopically, the first portion of blood (which is placed in first set 52 of sample chambers) is allowed to settle such as to form a monolayer of cells, e.g., using techniques as described in U.S. Pat. No. 9,329,129 to Pollack, which is incorporated herein by reference. It is noted that, in the context of the present application, the term monolayer is used to mean a layer of cells that have settled, such as to be disposed within a single focus field of the microscope. Within the monolayer there may be some overlap of cells, such that within certain areas there are two or more overlapping layers of cells. For example, red blood cells may overlap with each other within the monolayer, and/or platelets may overlap with, or be disposed above, red blood cells within the monolayer.

For some applications, die microscopic analysis of the first portion of the blood sample is performed with respect to the monolayer of cells. Typically, the first portion of the blood sample is imaged under brightfield imaging, i.e., under illumination from one or more light sources (e.g., one or more light emitting diodes, which typically emit light at respective spectral bands). Further typically, the first portion of the blood sample is additionally imaged under fluorescent imaging. Typically, the fluorescent imaging is performed by exciting stained objects (i.e., objects that have absorbed the stain(s)) within the sample by directing light toward the sample at known excitation wavelengths (i.e., wavelengths at which it is known that stained objects emit fluorescent light if excited with light at those wavelengths), and detecting the fluorescent light. Typically, for the fluorescent imaging, a separate set of light sources (e.g., one or more light emitting diodes) is used to illuminate the sample at the known excitation wavelengths.

As described with reference to US 2019/0302099 to Pollak, which is incorporated herein by reference, for some applications, sample chambers belonging to set 52 (which is used for microscopy measurements) have different heights from each other, in order to facilitate different measurands being measured using microscope images of respective sample chambers, and/or different sample chambers being used for microscopic analysis of respective sample types. For example, if a blood sample, and/or a monolayer formed by the sample, has a relatively low density of red blood cells, then measurements may be performed within a sample chamber of the sample carrier having a greater height (i.e., a sample chamber of the sample carrier having a greater height relative to a different sample chamber having a relatively lower height), such that there is a sufficient density of cells, and/or such that there is a sufficient density of cells within the monolayer formed by the sample, to provide statistically reliable data. Such measurements may include, for example red blood cell density measurements, measurements of other cellular attributes, (such as counts of abnormal red blood cells, red blood cells that include intracellular bodies (e.g., pathogens, Howell-Jolly bodies), etc.), and/or hemoglobin concentration. Conversely, if a blood sample, and/or a monolayer formed by the sample, has a relatively high density of red blood cells, then such measurements may be performed upon a sample chamber of the sample carrier having a relatively low height, for example, such that there is a sufficient sparsity of cells, and/or such that there is a sufficient sparsity of cells within the monolayer of cells formed by the sample, that the cells can be identified within microscopic images. For some applications, such methods are performed even without the variation in height between the sample chambers belonging to set 52 being precisely known.

For some applications, based upon the measurand that is being measured, the sample chamber within the sample carrier upon which to perform optical measurements is selected. For example, a sample chamber of the sample carrier having a greater height may be used to perform a white blood cell count (e.g., to reduce statistical errors which may result from a low count in a shallower region), white blood cell differentiation, and/or to detect more rare forms of white blood cells. Conversely, in order to determine mean corpuscular hemoglobin (MCH), mean corpuscular volume (MCV), red blood cell distribution width (RDW), red blood cell morphologic features, and/or red blood cell abnormalities, microscopic images may be obtained from a sample chamber of the sample carrier having a relatively low height, since in such sample chambers the cells are relatively sparsely distributed across the area of the region, and/or form a monolayer in which the cells are relatively sparsely distributed. Similarly, in order to count platelets, classify platelets, and/or extract any other attributes (such as volume) of platelets, microscopic images may be obtained from a sample chamber of the sample carrier having a relatively low height, since within such sample chambers there are fewer red blood cells which overlap (fully or partially) with the platelets in microscopic images, and/or in a monolayer.

In accordance with the above-described examples, it is preferable to use a sample chamber of the sample carrier having a lower height for performing optical measurements for measuring some measurands within a sample (such as a blood sample), whereas it is preferable to use a sample chamber of the sample carrier having a greater height for performing optical measurements for measuring other measurands within such a sample. Therefore, for some applications, a first measurand within a sample is measured, by performing a first optical measurement upon (e.g., by acquiring microscopic images of) a portion of the sample that is disposed within a first sample chamber belonging to set 52 of the sample carrier, and a second measurand of the same sample is measured, by performing a second optical measurement upon (e.g., by acquiring microscopic images of) a portion of the sample that is disposed within a second sample chamber of set 52 of the sample carrier. For some applications, the first and second measurands are normalized with respect to each other, for example, using techniques as described in US 2019/0145963 to Zait, which is incorporated herein by reference.

Typically, in order to perform optical density measurements upon the sample, it is desirable to know the optical path length, the volume, and/or the thickness of the portion of the sample upon which the optical measurements were performed, as precisely as possible. Typically, an optical density measurement is performed on the second portion of the sample (which is typically placed into second set 54 of sample chambers in an undiluted form). For example, the concentration and/or density of a component may be measured by performing optical absorption, transmittance, fluorescence, and/or luminescence measurements upon the sample.

Referring again to FIG. 3B, for some applications, sample chambers belonging to set 54 (which is used for optical density measurements), define at least a first region 56 (which is typically deeper) and a second region 58 (which is typically shallower), the height of the sample chambers varying between the first and second regions in a predefined manner, e.g., as described in US 2019/0302099 to Pollak, which is incorporated herein by reference. The heights of first region 56 and second region 58 of the sample chamber are defined by a lower surface that is defined by the glass sheet and by an upper surface that is defined by the molded component. The upper surface at the second region is stepped with respect to the upper surface at the first region. The step between the upper surface at the first and second regions, provides a predefined height difference Δh between the regions, such that even if the absolute height of the regions is not known to a sufficient degree of accuracy (for example, due to tolerances in the manufacturing process), the height difference Δh is known to a sufficient degree of accuracy to determine a parameter of the sample, using the techniques described herein, and as described in US 2019/0302099 to Pollak, which is incorporated herein by reference. For some applications, the height of the sample chamber varies from the first region 56 to the second region 58, and the height then varies again from the second region to a third region 59, such that, along the sample chamber, first region 56 defines a maximum height region, second region 58 defines a medium height region, and third region 59 defines a minimum height region. For some applications, additional variations in height occur along the length of the sample chamber, and/or the height varies gradually along the length of the sample chamber.

As described hereinabove, while the sample is disposed in the sample carrier, optical measurements are performed upon the sample using one or more optical measurement devices 24. Typically, the sample is viewed by the optical measurement devices via the glass layer, glass being transparent at least to wavelengths that are typically used by the optical measurement device. Typically, the sample carrier is inserted into optical measurement unit 31, which houses the optical measurement device while the optical measurements are performed. Typically, the optical measurement unit houses the sample carrier such that the molded layer is disposed above the glass layer, and such that the optical measurement unit is disposed below the glass layer of the sample carrier and is able to perform optical measurements upon the sample via the glass layer. The sample carrier is formed by adhering the glass layer to the molded component. For example, the glass layer and the molded component may be bonded to each other during manufacture or assembly (e.g. using thermal bonding, solvent-assisted bonding, ultrasonic welding, laser welding, beat staking, adhesive, mechanical clamping and/or additional substrates). For some applications, the glass layer and the molded component are bonded to each other during manufacture or assembly using adhesive layer 46.

In accordance with some applications of the present invention, a portion of a blood sample that comprises a cell suspension is placed within a sample chamber that is a cavity 55 that includes a base surface 57 (shown in FIG. 3C). In accordance with respective applications, the cavity is a closed (i.e., covered) cavity, or is an open (i.e., uncovered) cavity. For example, as described hereinabove, the first portion of the blood sample is typically placed in first set 52 of the sample chambers. For some applications, the first portion of the blood sample is placed in first set 52 of the sample chambers, subsequent to the first portion of the blood sample having been diluted. Typically, the cells in the cell suspension are allowed to settle on the base surface of the sample chamber to form a monolayer of cells on the base surface of the sample chamber. As noted hereinabove, in the context of the present application, the term monolayer is used to mean a layer of cells that have settled, such as to be disposed within a single focus field of the microscope (referred to herein as “the monolayer focus field”). Within the monolayer there may be some overlap of cells, such that within certain areas there are two or more overlapping layers of cells. For example, red blood cells may overlap with each other within the monolayer, and/or platelets may overlap with, or be disposed above, red blood cells within the monolayer.

Subsequent to the cells having been left to settle on the base surface of the sample chamber (e.g. by having been left to settle for a predefined time interval), at least one microscopic image of at least a portion of the monolayer of cells is typically acquired. Typically, a plurality of images of the monolayer are acquired, each of the images corresponding to an imaging field that is located at a respective, different area within the imaging plane of the monolayer. Typically, an optimum depth level at which to focus the microscope in order to image the monolayer is determined, e.g., using techniques as described in U.S. Pat. No. 10,176,565 to Greenfield, which is incorporated herein by reference. For some applications, respective imaging fields have different optimum depth levels from each other. For some applications, platelets that have settled within the monolayer are identified within the at least one microscopic image of at least a portion of the monolayer of cells.

The inventors of the present application have noticed that it is often the case that, even after having been left to settle such as to form a monolayer using the techniques described herein, not all of the platelets within a blood sample settle within the monolayer, and some cells continue to be suspended within the cell solution. More specifically, the inventors have found that it is typically the case that, even after the sample has been left to settle for approximately two minutes, between 10 percent and 70 percent of the platelets within the sample do not settle within the monolayer focus field. Typically, if the monolayer is allowed to form over a longer time period, then more platelets settle within the monolayer focus field. However, the inventors have found that even if the monolayer is allowed to form over a relatively long time period (e.g., between 15 and 30 minutes), some platelets still remain suspended within the solution such that the platelets are not disposed within the monolayer focus field. Typically, the number of platelets that remain suspended within the solution (such that the platelets are not disposed within the monolayer focus field) is dependent on the time for which the monolayer is allowed to form, in addition to the height of the cavity in which the cell solution is placed.

Therefore, for some applications, in order to accurately estimate the number of platelets in the sample, platelets that are suspended within the cell solution are identified, in addition to identifying platelets within the monolayer focus field. Typically, such platelets are identified by focusing the microscope at additional depth levels to the depth level(s) to which the microscope is focused in order to image the monolayer of cells (referred to herein as “the monolayer depth level(s)”), and acquiring images at the additional depth levels. Typically, the platelets within the images that are acquired at the additional depth levels are identified and counted, and, based upon the count of platelets within those images, a total count of the platelets that are suspended within the cell solution is estimated.

As described hereinabove, typically, the platelets that are suspended within the cell solution are identified by acquiring microscopic images at additional depth levels. Typically, the height interval between successive additional depth levels at which the cell solution is imaged is dependent upon the depth of focus of the microscope optical system. For example, depending upon the depth of focus of the microscope optical system, the microscope may be focused at additional depth levels that are separated from each other by a given height difference (e.g., between 1 micron and 10 microns), over the height of the portion of the sample that is within the sample chamber. Typically, within the monolayer depth level(s), microscopic images of the sample chamber are acquired from a relatively large number of imaging fields, as described hereinabove. For example, microscopic images of tire monolayer may be acquired from between 100 and 500 imaging fields. Typically, between 5 and 100 (e.g., between 10 and 50) of these imaging fields are optimized for identifying platelets, by acquiring these images at an increased exposure time relative to other images. For some applications, for each of the additional depth levels, microscopic images are acquired from only a subset of the imaging fields, in order to reduce the amount of time that it takes to image the portion of the sample relative to if microscopic images are acquired from all of the imaging fields. For example, microscopic images from between 3 and 10 imaging fields may be acquired within each of the additional depth levels. For some applications, the ratio of (a) the number of imaging fields at which the monolayer is imaged and that are optimized for identifying platelets (e.g., by having an increased exposure time, as described above) to (b) the number of imaging fields at which each of the additional depth levels is imaged, is between 2:1 and 10:1. For some applications, the ratio is 1:1.

For some applications, the portion of the sample is imaged at the additional depth levels under brightfield imaging, e.g., as described hereinabove. Alternatively or additionally, the portion of the sample is imaged at the additional depth levels under fluorescent imaging, e.g., as described hereinabove. For some applications, the first portion of the sample is stained with one or more stains that cause platelets within the sample to be visible under bright field imaging conditions and/or under fluorescent imaging conditions, e.g., as described hereinabove. For example, the first portion of the sample may be stained with methylene blue and/or Romanowsky stains. For some applications, images having imaging parameters that are not necessarily optimized for platelet detection are acquired at the additional depth levels, for example, in order to detect other entities, which may otherwise be confused with platelets.

Reference is now made to FIGS. 4A and 4B, which are microscope images acquired from the monolayer depth level under brightfield imaging using respective imaging parameters, in accordance with some applications of the present invention. As may be observed, a platelet 60 is identifiable within the images, and the platelet is surrounded by erythrocytes 61. The erythrocytes are in focus, since the images were acquired at the monolayer depth level, within which the erythrocytes are settled. Reference is also made to FIG. 5 , which is a fluoroscopic microscope image acquired from the monolayer depth level, in accordance with some applications of the present invention. Again, a platelet 60 is identifiable within the images, and the platelet is surrounded by erythrocytes, which are faintly visible.

Reference is additionally made to FIGS. 6A and 6B, which are microscope images acquired from an additional depth level (i.e., not the monolayer depth level) under brightfield imaging, using respective imaging parameters, in accordance with some applications of the present invention. As may be observed a platelet 60 is identifiable within the images, and erythrocytes are visible in the background. The erythrocytes are out of focus since the images were not acquired at the monolayer depth level within which the erythrocytes have settled. Reference is also made to FIG. 7 , which is a fluoroscopic microscope image acquired from the additional depth level in accordance with some applications of the present invention. Again, a platelet 60 is identifiable within the images.

Typically, platelets that have not settled within the monolayer are identified within the images that are acquired at the additional depth levels. (It is noted the identified platelets may include platelets that are out of focus within the additional depth levels.) Further typically, based upon the platelets that are identified within the images that are acquired at the additional depth levels, a count of the platelets that have not settled within the monolayer is estimated. For some applications, in order to perform the above-described estimate, the computer processor is configured to avoid duplicate counts of platelets within images that are acquired at adjacent depth levels, by identifying platelets within images that are acquired at adjacent depth levels that are disposed at similar locations to each other within the imaging plane and determining whether the platelets as identified at each of the depth levels are likely to correspond to a single (i.e., the same) platelet. For some applications, in determining whether the platelets as identified at each of the adjacent depth levels are likely to correspond to a single (i.e., the same) platelet, the computer processor accounts for lateral movement of the platelets between the images acquired at each of the adjacent depth levels. For some applications, in order to perform the above-described estimate, the computer processor is configured to account for interference with the visibility of platelets by white blood cells that are disposed within the monolayer and/or that are suspended within the cell solution. For example, within fluorescent images that am acquired at the additional depth levels, white blood cells that fluoresce within the monolayer are typically visible and interfere with the visibility of platelets that are disposed above the white blood cells. Therefore, platelets that are disposed above white blood cells within the monolayer may be excluded from the platelet count. Since platelets within the volumes above white blood cells am excluded from the count, the number of platelets within these volumes may be estimated. Alternatively or additionally, in order to perform the above-described estimate, the computer processor is configured to account for interference with the visibility of platelets by red blood cells that are disposed within the monolayer, and that may interfere with the identification of platelets within bright field images.

For some applications, counts of platelets within the monolayer depth level and/or within the additional depth levels are normalized, and/or other statistical analysis techniques are applied to one or both of these counts. For example, the count of the platelets within a given imaging field may be normalized with respect to the red blood cell count within that field, the time dynamics of the settling of the platelets may be incorporated into the estimate of platelets that are not settled within the monolayer, and/or outliers may be removed from the estimates. For some applications, additional imaging fields are imaged, if there is a low platelet count, if there arc outlier fields (e.g., with very high or very low platelet counts), and/or if imaging fields that are imaged at the additional depth levels are rejected due to errors.

For some applications, a count of the platelets that have settled within the monolayer is compared to a count of the platelets that have not settled within the monolayer. Typically, an output is generated in response to the comparison. For some applications, a clinical condition is derived and outputted to a user, based upon tire comparison of the count of the platelets that have settled within the monolayer and the count of the platelets that have not settled within the monolayer. For example, the extent of platelet activation within the sample may be derived, at least partially based upon the comparison. Alternatively or additionally, a clinical condition may be derived based upon the size, shape, settling time, and/or settling dynamics of the platelets. For some such applications, the settling dynamics of the platelets are determined by imaging the same imaging field a plurality of times, with a lime interval between each of the image acquisitions, and/or by determining until what height within the sample chamber platelets are present at a given time.

For some applications, the computer processor generates an output indicating that the sample should be prepared in a different way to how it was prepared (e.g., by modifying the diluent within which the sample is diluted, by adding a platelet activation agent, and/or by adding a coagulation agent), based upon the comparison.

For some applications, based upon the comparison between the count of the platelets that have settled within the monolayer and the count of the platelets that have not settled within the monolayer, the portion of the blood sample is invalidated from being used for performing at least some measurements upon the sample. For example, if the ratio of unsettled platelets to settled platelets is greater than a First given threshold, and/or lower than a second given threshold, then this might be interpreted as being indicative of a problem with the sample and/or the preparation thereof.

For some applications, a parameter of the sample (such as platelet volume, mean platelet volume, and/or median platelet volume) is determined based upon a measurement that is performed upon the first portion of the sample. For some applications, the measurement is calibrated, based upon the comparison between properties of the platelets that have settled within the monolayer and properties of the platelets that have not settled within the monolayer.

Reference is now made to FIG. 8 and FIG. 9 , which are flowcharts showing step of methods that are performed with respect to platelets within a blood sample, in accordance with some applications of the present invention. For some applications, a cell suspension is placed within a sample chamber (step 70) and allowed to settle to form a monolayer (step 71). Subsequently, at least one image is acquired while the microscope is focused at the monolayer-depth-level (step 72), and platelets that have settled within the monolayer are identified in the image (step 74). Additionally, at least one microscopic image of the sample is acquired, while the microscope is focused at a different depth level from the monolayer-depth-level (step 73). and platelets that have not settled within the monolayer are identified within the at least one microscopic image at the different depth level from the monolayer-depth-level (step 75). An output at least partially based upon the platelets identified as having settled within the monolayer and the platelets identified as not having settled within the monolayer, is generated (step 79), as shown. For some applications, as shown in FIG. 9 . following identifying the platelets in the images (steps 74 and 75), a first platelet count of platelets that have settled within the monolayer is determined (step 76), and a second count of platelets that have not settled within the monolayer is determined (step 77). An output is then generated (step 78) based upon the first and second platelet counts. For example, an output may be generated based on a comparison between the first and second platelet counts, in accordance with the methods described hereinabove.

In general, it is noted that although some applications of the present invention have been described with respect to platelets within a blood sample, the scope of the present invention includes applying the apparatus and methods described herein to a variety of entities within a variety of samples, mutatis mutandis. For example, the apparatus and methods that are described with reference to identifying platelets that have not settled within a monolayer may be performed with respect to other entities within a blood sample, mutatis mutandis. Such entities may include white blood cells, anomalous white blood cells, circulating tumor cells, red blood cells, reticulocytes, Howell-Jolly bodies, foreign bodies (such as bacteria, fungi, yeast or parasites), entities that are added to a diluent (such as beads), etc.

Reference is now made to FIG. 10 , which is a flowchart showing steps of a method that is performed with respect entities within a blood sample, in accordance with some applications of the present invention. As described hereinabove with reference to FIGS. 8 and FIG. 9 , a cell suspension is placed within a sample chamber (step 70) and allow ed to settle to form a monolayer (step 71). Subsequently, at least one image is acquired while the microscope is focused at the monolayer-depth-level (step 72), and entities of a given type are identified in the image (step 92). Additionally, at least one microscopic image of the sample is acquired, while the microscope is focused at a different depth level front the monolayer-depth-level (step 73), and entities of the given type that have not settled within the monolayer are identified within the at least one microscopic image at the different depth level from the monolayer-depth-level (step 94). An output at least partially based upon the entities of the given type identified as having settled within the monolayer and the entities of the given type identified as not having settled within the monolayer, is generated, as shown (step 96).

For some applications, the apparatus and methods described herein are applied to a biological sample, such as, blood, saliva, semen, sweat, sputum, vaginal fluid, stool, breast milk, bronchoalveolar lavage, gastric lavage, tears and/or nasal discharge, mutatis mutandis. The biological sample may be from any living creature, and is typically from warm blooded animals. For some applications, the biological sample is a sample from a mammal, e.g., from a human body. For some applications, the sample is taken from any domestic animal, zoo animals and farm animals, including but not limited to dogs, cats, horses, cows and sheep. Alternatively or additionally, the biological sample is taken from animals that act as disease vectors including deer or rats.

For some applications, the apparatus and methods described herein are applied to a non bodily sample. For some applications, the sample is an environmental sample, such as, a water (e.g. groundwater) sample, surface swab, soil sample, air sample, or any combination thereof, mutatis mutandis. In some embodiments, the sample is a food sample, such as, a meat sample, dairy sample, water sample, wash-liquid sample, beverage sample, and/or any combination thereof.

For some applications, the sample as described herein is a sample that includes blood or components thereof (e.g., a diluted or non-diluted whole blood sample, a sample including predominantly red blood cells, or a diluted sample including predominantly red blood cells), and parameters are determined relating to components in the blood such as platelets, white blood cells, anomalous white blood cells, circulating tumor cells, red blood cells, reticulocytes, Howell-Jolly bodies, etc.

Applications of the invention described herein can take the form of a computer program product accessible from a computer-usable or computer-readable medium (e.g., a non-transitory computer-readable medium) providing program code for use by or in connection with a computer or any instruction execution system, such as computer processor 28. For the purposes of this description, a computer-usable or computer readable medium can be any apparatus that can comprise, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The medium can be an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system (or apparatus or device) or a propagation medium. Typically, the computer-usable or computer loadable medium is a non-transitory computer-usable or computer readable medium.

Examples of a computer-readable medium include a semiconductor or solid state memory, magnetic tape, a removable computer diskette, a random-access memory (RAM), a read-only memory (ROM), a rigid magnetic disk and an optical disk. Current examples of optical disks include compact disk-read only memory (CD-ROM), compact disk-read/write (CD-R/W) and DVD.

A data processing system suitable for storing and/or executing program code will include at least one processor (e.g., computer processor 28) coupled directly or indirectly to memory elements (e.g., memory 30) through a system bus. The memory elements can include local memory employed during actual execution of the program code, bulk storage, and cache memories which provide temporary storage of at least some program code in order to reduce the number of times code must be retrieved from bulk storage during execution. The system can read the inventive instructions on the program storage devices and follow these instructions to execute the methodology of the embodiments of the invention.

Network adapters may be coupled to the processor to enable the processor to become coupled to other processors or remote printers or storage devices through intervening private or public networks. Modems, cable modem and Ethernet cards are just a few of the currently available types of network adapters.

Computer program code for carrying out operations of the present invention may be written in any combination of one or more programming languages, including an object-oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the C programming language or similar programming languages.

It will be understood that algorithms described herein, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general-purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer (e.g., computer processor 28) or other programmable data processing apparatus, create means for implementing the functions/acts specified in the algorithms described in the present application. These computer program instructions may also he stored in a computer-readable medium (e.g., a non-transitory computer-readable medium) that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable medium produce an article of manufacture including instruction means which implement the function/act specified in the flowchart blocks and algorithms. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the algorithms described in the present application.

Computer processor 28 is typically a hardware device programmed with computer program instructions to produce a special purpose computer. For example, when programmed to perform the algorithms described heroin, computer processor 28 typically acts as a special purpose sample-analysis computer processor. Typically, the operations described herein that are performed by computer processor 28 transform the physical state of memory 30, which is a real physical article, to have a different magnetic polarity, electrical charge, or the like depending on the technology of die memory that is used.

The apparatus and methods described herein may be used in conjunction with apparatus and methods described in any one of the following patents or patent applications, all of which are incorporated herein by reference:

U.S. Pat. No. 9,522,396 to Bachelet;

U.S. Pat. No. 10,176,565 to Greenfield;

U.S. Pat. No. 10,640,807 to Pollak;

U.S. Pat. No. 9,329,129 to Pollak:

U.S. Pat. No. 10,093,957 to Pollak;

U.S. Pat. No. 10,831,013 to Yorav Raphael;

U.S. Pat. No. 10,843,190 to Bachelet;

U.S. Pat. No. 10,482,595 to Yorav Raphael;

U.S. Pat. No. 10,488,644 to Eshel;

WO 17/168411 to Eshel;

US 2019/0302099 to Pollak;

US 2019/0145963 to Zait; and

WO 19/097387 to Yorav-Raphael.

It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modification thereof that are not in the prior art, which would occur to persons skilled in the art upon reading the foregoing description. 

1. A method comprising: placing at least a portion of a blood sample that is a cell suspension within a sample chamber that is a cavity that includes a base surface; allowing the cells in the cell suspension to settle on the base surface of the sample chamber to form a monolayer of cells on the base surface of the sample chamber; acquiring at least one first microscopic image of at least a portion of the monolayer of cells, using a microscope while the microscope is focused at a monolayer-depth-level, at which the monolayer is within focus of the microscope; identifying platelets that have settled within the monolayer, within the at least one microscopic image; based upon the platelets that are identified within the at least one microscopic image, determining a first platelet count of platelets that have settled within the monolayer; acquiring at least one additional microscopic image of the portion of the sample using the microscope, while the microscope is focused at a different depth level from the monolayer-depth-level; identifying platelets that have not settled within the monolayer, within the at least one additional microscopic image; based upon the platelets that are identified within the at least one additional microscopic image, determining a second platelet count of platelets that have not settled within the monolayer; and generating an output based upon the first and second platelet counts.
 2. The method according to claim 1, further comprising deriving an error with the blood sample at least partially based upon comparing the first and second platelet counts to each other, wherein generating the output comprises generating an indication of the error.
 3. The method according to claim 1, further comprising deriving an error with preparation of the blood sample at least partially based upon comparing the first and second platelet counts to each other, wherein generating the output comprises generating an indication of the error.
 4. The method according to claim 1, further comprising deriving a clinical condition of the subject at least partially based upon comparing the first and second platelet counts to each other, wherein generating the output comprises generating an indication of the clinical condition.
 5. The method according to claim 1, further comprising deriving a measure of platelet activation at least partially based upon comparing the first and second platelet counts to each other, wherein generating the output comprises generating an indication of the platelet activation.
 6. The method according to claim 1, wherein identifying platelets that have not settled within the monolayer within the at least one additional microscopic image comprises accounting for interference with visibility of platelets by white blood cells that are disposed within the monolayer.
 7. The method according to claim 1, wherein identifying platelets that have not settled within the monolayer within the at least one additional microscopic image comprises accounting for interference with visibility of platelets by red blood cells that are disposed within the monolayer.
 8. The method according to claim 1, wherein: acquiring the at least one first microscopic image of the portion of the monolayer of cells comprises acquiring a first number of images of the monolayer at respective imaging fields while the microscope is focused at one or more monolayer-depth-levels, at which the monolayer is within focus of the microscope; acquiring the at least one additional microscopic image of the portion of the sample comprises acquiring a second number of images at respective imaging fields, while the microscope is focused at the different depth level from the monolayer-depth-level; and a ratio between the first number and the second number is greater than 2:1.
 9. The method according to claim 1, wherein: acquiring the at least one additional microscopic image of the portion of the sample comprises acquiring a plurality of additional microscopic images, while the microscope is focused at respective different depth levels from the monolayer-depth-level; and identifying platelets that have not settled within the monolayer within the at least one additional microscopic image comprises avoiding duplicate counts of platelets within images that are acquired at adjacent depth levels.
 10. The method according to claim 9, wherein avoiding duplicate counts of platelets within images that are acquired at adjacent depth levels comprises accounting for lateral movement of platelets between acquisitions of the images that are acquired at adjacent depth levels.
 11. A method comprising: placing at least a portion of a blood sample that is a cell suspension within a sample chamber that is a cavity that includes a base surface; allowing the cells in the cell suspension to settle on the base surface of the sample chamber to form a monolayer of cells on the base surface of the carrier; acquiring at least one microscopic image of at least a portion of the monolayer of cells, using a microscope while the microscope is focused at a monolayer-depth-level, at which the monolayer is within focus of the microscope; identifying platelets that have settled within the monolayer, within the at least one microscopic image; acquiring at least one additional microscopic image of the portion of the sample using the microscope, while the microscope is focused at a different depth level from the monolayer-depth-level; identifying platelets that have not settled within the monolayer, within the at least one additional microscopic image; and generating an output at least partially based upon the platelets identified as having settled within the monolayer and the platelets identified as not having settled within the monolayer.
 12. The method according to claim 11, further comprising estimating a platelet count for the blood sample based upon the platelets identified as having settled within the monolayer and the platelets identified as not having settled within the monolayer, wherein generating the output comprises generating an indication of the platelet count.
 13. The method according to claim 11, further comprising deriving a platelet-settling characteristic of the sample based upon the platelets identified as having settled within the monolayer and the platelets identified as not having settled within the monolayer, wherein generating the output comprises generating an indication of the platelet-settling characteristic.
 14. The method according to claim 11, further comprising deriving a characteristic of platelets within the sample based upon a combination of the platelets identified as having settled within the monolayer and the platelets identified as not having settled within the monolayer, wherein generating the output comprises generating an indication of the derived characteristic. 15.-17. (canceled)
 18. Apparatus comprising: a sample chamber that is a cavity that includes a base surface and that is configured to receive at least a portion of a blood sample that is a cell suspension and to allow the cells in the cell suspension to settle on the base surface of the sample chamber to form a monolayer of cells on the base surface of the sample chamber; a microscope configured to acquire: at least one first microscopic image of at least a portion of the monolayer of cells, while the microscope is focused at a monolayer-depth-level, at which the monolayer is within focus of the microscope, and at least one additional microscopic image of the portion of the sample, while the microscope is focused at a different depth level from the monolayer-depth-level; and a computer processor configured to: identify platelets that have settled within the monolayer, within the at least one first microscopic image, identify platelets that have not settled within the monolayer, within the at least one additional microscopic image, and generate an output at least partially based upon the platelets identified as having settled within the monolayer and the platelets identified as not having settled within the monolayer.
 19. (canceled) 